In the use of sensors, for example radar, it may be desirable to use a sensor to cover a greater area than the range of the sensor allows. A common way of achieving such increased coverage is to arrange the sensor on a mobile platform, the platform then being moved in such a manner that the desired area is covered. Aircraft, ships and cars may be cited as examples of platforms for sensors.
In the case of the above mentioned type of movement with a sensor platform, a problem arises regarding how the platform is to be moved in order to achieve the desired coverage. This problem may arise in particular if the range of the sensor is not symmetrical. If the sensor is a radar system, this problem may arise above all in connection with so-called group antennas, in other words antennas with an antenna pattern or pointing direction that is controlled electrically, since such antennas often have a range which is angle-dependent at least in one plane. The range of the sensor may, however, be symmetrical in the plane in which the range is angle-dependent.
U.S. Pat. No. 4,129,866 discloses a method of solving a similar problem for a radar system with its antenna arranged on top of an aircraft. In the solution that is described, the carrier aircraft is flown along a sinusoidal path in relation to the ground plane. This may be said to create disadvantages since the pointing direction of the antenna in the vertical direction will vary in an undesirable manner in connection with the turns of the aircraft.
Other known solutions are described in, inter alia, U.S. Pat. No. 5,097,267, U.S. Pat. No. 4,779,097 and U.S. Pat. No. 5,357,259. These specifications disclose methods of solving coverage problems in connection with group antennas mounted on aircraft. All the solutions described in these specifications comprise mechanical steering of the antennas in relation to the platform, which may be said to lead to complex and thus expensive solutions.